Molten metal pumps

ABSTRACT

A pump having a pumping chamber, an impeller shaft enclosed in a shaft bore communicating with the chamber, and an impeller carried on a shaft in the chamber is partially immersed in liquid so that the shaft bore extends down to the chamber from a location above the liquid, and the shaft bore is pressurized with an inert gas to counteract the pressure of the liquid head and the pumping pressure and thereby prevent the liquid from rising in the bore around the shaft.

United States atent [191 Koch [ MOLTIEN METAL PUMPS lFenton C. Koch,Chesterland, Ohio [73] Assignee: High Temperature Systems, 1nc.,Newbury, Ohio [22] Filed: Oct. 17, 1972 [21] App]. No.: 298,415

[75] Inventor:

[52] 11.5. C1 415/175, 415/200, 415/214 [51] 1nt. C1. F04d 7/00, F04d7/02, F04d 29/10 [58] Field of Search 415/200, 175, 214

[56] References Cited UNITED STATES PATENTS 2,528,210 10/1950 Stewart415/214 3,048,384 8/1962 Sweeney et a1. 415/214 FOREIGN PATENTS ORAPPLICATIONS 788,831 1/1958 Great Britain 415/175 Sept. 17, 1974 s7/1929 Germany ..415/214 11/1955 Netherlands ..415/175 PrimaryExaminer-Henry F. Raduazo Attorney, Agent, or Fir'm-Watts, Hoffmann,Fisher & Heinke Co.

[5 7 ABSTRACT A pump having a pumping chamber, an impeller shaftenclosed in a shaft bore communicating with the chamber, and an impellercarried on ashaft in the chamber is partially immersed in liquid so thatthe shaft bore extends down to the chamber from a location above theliquid, and the shaft bore is pressurized with an inert gas tocounteract the pressure of the liquid head and the pumping pressure andthereby prevent the liquid from rising in the bore around the shaft.

1 im 6 Wavin lis te MENIEDSEP 1 719m SHEU @1331 OF 3 1 I 3 1 ///fi Y 4 5fin //p Q/ o o o o f MOLTEN METAL lP'UMlPS BACKGROUND OF THE INVENTIONThis invention relates generally to the pumping art, and morespecifically to apparatus and method for lifting, conveying orcirculating high temperature and/or corrosive materials such as moltenaluminum, zinc and the like.

The present state of the art makes the handling of molten metals with acentrifugal pump very expensive and somewhat impractical. Presently usedmolten metal pumps are assembled from many different parts of severaldifferent refractory materials. These different parts are commonlycemented together or fitted together with threaded connections. Thevarious parts of these presently used pumps are not subjected to thesame degree of abrasive wear, mechanical strain, corrosive attack by themolten metal at elevated temperatures, oxidation from exposure to thehigh temperature air in the metal container at the interface of themolten metal and the atmosphere or thermal shock during immersion of thepump and during its operation.

The drive shaft of a molten metal pump in a typical molten metalcontainer connects the impeller located below the molten metal surfaceto the drive motor located above the molten metal surface. For thisreason the pump drive shaft rotates at the interface between the moltenmetal and the high temperature air in the molten metal container. Theshaft, rotating at this point, constantly stirs a mixture of hightemperature metal and high temperature air forming large amounts of theoxide on the metal commonly called skim or dross. This dross itselfconstitutes a serious loss, but in addition not only wears away theshaft at the metal air interface during rotation because of its abrasivecharacter but presents a substantial disposal problem.

The support members and the discharge tube in pumps of present art aresubjected to severe but different rates of deterioration. Neither ofthese parts rotate but are subjected to oxidation, corrosion, thermalshock and mechanical abuse.

For these explained reasons, the useful lives of the various parts ofthe pumps presently used are not of equal length. Failure ofa partcannot be predicted, and when it occurs in service it is almost alwaysduring pump operation. Because of the basic structural weakness ofcemented and threaded joints in a refractory pump, any part breakageusually results in a multiple part failure that requires a complete pumpoverhaul.

A large stock of many different refractory pump parts as well as sparecomplete pumps are required to assure even intermittent operation. Thisfact is a severe detriment to a more universal use of molten metalpumps.

The deficiencies of the present state of the art are well known and havebeen well known for a long period of time. In spite of this, the presentpumps available do not fill the need for a simple, reliable andpractical method for pumping molten metal and high temperature moltenmaterial.

SUMMARY OF THE INVENTION An object of the present invention is toprovide pumping apparatus and methods for handling molten, hightemperature and/or corrosive materials.

Another object of the present invention is to provide a pumpcharacterized by a rotating impeller shaft enclosed in a shaft boreextending down into a liquid bath and means for pressurizing the shaftbore with an inert gas in order to prevent the liquid from rising in thebore around the shaft.

A more specific object of the present invention is to provide a pumphaving structure defining a pump chamber, a shaft bore and a dischargebore communicating with the chamber, a shaft extending through the shaftbore, an impeller carried on the shaft in the chamber for pumping liquidthrough the discharge bore, and means for supplying an inert gas underpressure to the shaft bore around the shaft so that liquid in the pumpchamber is prevented from rising in the shaft bore around the shaft.

Still another object of the invention is to provide a pump as describedin any of the preceding paragraphs which is further characterized by aninlet opening extending through the wall of the shaft bore into itsinte- A further object of the present invention is to provide a pumpincluding structure extending down into liquid in a reservoir anddefining a pump chamber having an inlet opening below the liquid level,a shaft bore and a discharge bore communicating with the chamber, ashaft enclosed in the shaft bore and extending down to the pump chamberfrom a location above the liquid, an impeller on the shaft in the pumpchamber, and means for supplying an inert gas to the shaft bore at apressure sufficient to counteract the pumping pressure and the pressureof the liquid head so that liquid is prevented from rising in the shaftbore around the shaft.

A further object of the present invention is to provide a method ofpumping liquid using a pump as described in any of the precedingparagraphs and comprising the steps of immersing part of the pumpincluding the pump chamber in a liquid so that the shaft bore extendsfrom a location above the liquid and pressurizing the shaft bore with aninert gas at a pressure sufficient to counteract the pumping pressureand the pressure of the liquid head so that the liquid is prevented fromrising in the shaft bore around the shaft.

Still another object of the present invention is to provide a pump asdescribed in any of the preceding paragraphs which is furthercharacterized by a construction requiring no structural supports ordischarge tube, thus eliminating cemented or threaded structural joints.

Still another objective of this invention is a pump having the shaftbore and discharge bore located to equalize their lives in spite oftheir exposure to different degrees of deterioration, resulting inlonger useful pump life and reducing the possibility of massive pumpdamage by sudden individual part failure.

Other objects and a fuller understanding of the invention will beapparent from the following detailed description and the accompanyingdrawings.

DESCRIPTION or THE DRAWINGS FIG. I is an elevation view of a pumpresulting from the present invention with parts sectionally broken awaybelow the molten material line.

FIG. 2 is a bottom view of the pump resulting from this inventionshowing the pump body, bottom plate and impeller in position.

FIG. 3 is a sectional view showing the pump body, impeller, dischargebore and connecting chamber in position.

FIG. 4 is a sectional view showing the pump body, shaft bore anddischarge bore in position.

FIG. 5 is a sectional of a pump resulting from this invention providinga discharge for the molten material below the surface of the moltenmaterial in the pot or container.

FIG. 6 is a sectional view of a pump resulting from this inventionproviding an inlet for the molten material above the bottom of the pump.

DETAILED DESCRIPTION OF INVENTION FIG. 1 shows a molten metal bath 1containing one embodiment ofa pump according to the present invention.It can be readily understood that the specific details of the containeror pot would be dependent on the character of the molten material andthe specific work being done on or by the molten material and the pump.that is the subject of this invention. Because of this,

there is no reason or need to describe the container in detail.

The pump body 2 is held in a partially submerged position in the moltenmaterial by the superstructure 4. The superstructure 4 may be anassembly of metal or like material that fits the upper surface of thepump body 2, that has a drive motor mount as a part and has holes bored,machined or made in some like manner to suit the bores provided in thepump body 2 for the shaft 13 and discharge 9. The superstructure 4 alsomay have holes provided to attach a pillow block assembly 16 and adischarge tube 17 using bolts 15 or other means.

If the density of the molten material is less than the effective densityof the pump, the pump can be held by a suitable hook, chain or cableattached to the superstructure 4 and is usually held somewhat above thebottom of the molten material container. If the molten material bath ismore dense and the pump tends to float, the pump must be held inposition by suitable brackets attached to the superstructure 4 and themolten material bath container.

The pump body 2 as shown is circular in cross section. It should beeasily understood, however, that the pump body 2 could as easily beanother shape in cross section such as a square, octagon or ellipse.

A shaft bore 8 and a discharge bore 9 are shown provided verticallythrough the pump body 2. A pump chamber 11 is defined by an axial bore10 which opens on the bottom of the pump body 2 and connects with theshaft bore 8 and the discharge bore 9. The pump chamber 11 provides achamber for impeller rotation. A pump drive shaft 13 and impeller 3 areshown in position connected to a drive motor 14 by a suitable connection21. The drive motor 14 can be air, hydraulic, electric or driven byother suitable means. A pillow block 16 or some other suitable deviceprovides a top bearing support for the connection 21 between the drivemotor 14 and the drive shaft 13. This pillow block may be pressure tightor may permit sufficient passage of gas to cool its bearings. An inertor fluxing gas may be introduced through tubing 18 and a fitting 19 orother suitable means through the pillow block 16 into the shaft bore 8.The pressure of the inert or fluxing gas while maintained in the shaftbore 8 is controlled to provide a dry running shaft down to a bleed hole20 drilled radially between the outside of the pump body 2 and the shaftbore 8. Prior to or during operation of the pump, the pressure of theinert or fluxing gas is raised from atmospheric until bubbles or gas 22exit from bleed hole 20 and are observed on the surface of the moltenmaterial 1. A bottom plate 12 may be incorporated to provide a runningfit bearing for the impeller 3 and to seal the pump chamber 11 aroundthe impeller 3 from the material bath 1. The pump body 2 may beconstructed of materials that resist the chemical attack of the moltenmaterial bath 1. The shaft bore 8, discharge bore 9 and the bottom axialbore 10 may be cast in place, drilled, machined, bored or formed in someother suitable manner. It should be understood that the pump body 2 canbe made in other ways such as by building up cross sectional slabscemented together within the scope of this invention. The shaft 13 andimpeller 3 are constructed of materials resisting the effects ofoxidation, abrasion and erosion as well as the chemical attack of themolten material being pumped. It should be understood that a shaft 13and impeller 3 may be used in one piece or these parts may consist ofmany parts within the scope of this invention.

The bottom plate 12 may be constructed of material resistant to abrasionat the surface adjacent to the impeller 3 as well as the chemical attackof the molten material being pumped. In many cases all of these partsmay be constructed of the same material, simplifing construction. Itshould be understood, however, that different materials may besubstituted for or sections inserted in specific parts to eliminate orreduce localized wear.

The pump body 2 may be attached to the superstructure 4 with bolts 7threaded into the pump body 2. The pillow block 16 and the dischargetube 17 are shown attached to the pump body by the bolts 15 through thesuperstructure 4 and through gaskets 5 into the pump body 2. The gaskets5 of suitable material may be provided to maintain gas pressure in theshaft bore 8 and to prevent leakage of molten material from theconnection of the discharge bore 9 and the superstructure 4 and the pumpbody 2.

During operation of the pump resulting from this invention, the drivemotor 14 turns the impeller 3 through the connection 21 supported bypillow block 16 and drive shaft 13. It is to be understood that theconstruction of the drive shaft 13 and impeller 3 design are dictated bythe material being pumped and the requirements of the application andthat the illustrated impeller and shaft are only one example of aparticular way of constructing the pump of the present invention. Moltenmaterial enters the bottom of the-impeller 3 in FIG. 1 and is directedthrough the pumping chamber 11, up the discharge bore 9 and through thedischarge tube 17 or through additional tubing if required by theapplication. During operation, inert or fluxing gas pressure may bemaintained in the shaft bore 8, greatly reducing or eliminating theformation of dross around the drive shaft 13 and thereby greatlyreducing or eliminating the abrasive wear presently encountered insimilar pumps.

It should be easily understood from FIG. 3 and FIG. 4 that the shaftbore 8 and discharge bore 9 can be located at desirable locations,considering their exposure to wear and their useful lives. The pumpingchamber 11 may be provided to connect the discharge bore 9 to the outletof the impeller 3 and to increase efficiency.

It may be advantageous to provide a pump discharge below the surface ofthe molten bath by provision of a radial bore 23 into the discharge bore9 from the outside surface of the pump body 2 as shown in FIG. 5.

It may be advantageous to provide an inlet 24 for the molten materialabove the bottom of the pump body 2 and above the pump chamber 11 asillustrated in FIG. 6. An impeller 3 of suitable design may be requiredincorporating a closed bottom and an inlet in its top as shown.

I claim:

1. Pump apparatus adapted to be immersed in molten material and operatedto move the material, said apparatus comprising:

a. a vertically positionable hollow structure of refractory materialextendible down into the molten material and defining a submersible pumpchamber in the lower end, a shaft bore extending upwardly from said pumpchamber in said structure, and a discharge bore in said structurecommunicating with and extending upwardly from said pump chamber in thedirection of said shaft bore,

b. a shaft extending through said shaft bore,

c. motor means operatively connected to said shaft,

1. Pump apparatus adapted to be immersed in molten material and operatedto move the material, said apparatus comprising: a. a verticallypositionable hollow structure of refractory material extendible downinto the molten material and defining a submersible pump chamber in thelower end, a shaft bore extending upwardly from said pump chamber insaid structure, and a discharge bore in said structure communicatingwith and extending upwardly from said pump chamber in the direction ofsaid shaft bore, b. a shaft extending through said shaft bore, c. motormeans operatively connected to said shaft, d. an impeller on said shaftin said pump chamber, said shaft and impeller being of a refractorymaterial, e. said hollow structure having an inlet opening spaced abovesaid impeller so that during operation of said pump molten material isdrawn through said inlet opening into said pump chamber and is pumpedout through said discharge bore, and f. means for supplying andpressurizing said shaft bore with an inert gas so that molten materialentering said inelt opening is prevented from rising in said shaft borearound said shaft.